Frost Dates for 49455 — Shelby, Michigan

Half of springs at Hart 3 WSW, MI see their last 32°F night by May 12; only one in ten is past it by April 25, and one in ten still has one after May 28. Planting tender crops after May 20 leaves a 30% risk of a frost on them, after May 24 20%, and after May 28 10%. The 16 days between the even-odds date and the one-in-ten date is narrower than at 38% of the 172 Michigan stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 10 in half of years, as early as September 25 one year in ten, and holds off past October 26 one year in ten. A hard freeze of 28°F follows 15 days later, around October 25; in spring the one-in-ten date for 28°F is May 20, 8 days before the 32°F one. The freeze-free season lasts 151 days in a typical year, shorter than at 63% of the 172 Michigan stations; it reaches 174 days one year in ten and falls short of 129 one year in ten. On average 151 nights a year drop to 32°F or below. Nights of 36°F, when frost can still settle on leaves in low, open spots, continue 12 days longer, to about May 24, and return around September 29. Severe cold of 16°F or below comes every winter, usually between December 3 and March 24.

July is the warmest month at Hart 3 WSW, MI, averaging 80°F by day and 58°F at night; January is the coldest at 30°F and 16°F. A freezing night is all but certain in every month from October to April (a 90% chance or more). From June to August the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 78% of years.

Warmth for growing adds up to 2,267 growing degree days a year (base 50°F), fewer than at 59% of the 172 Michigan stations. 31% of them (706) have built up by the end of June, and July adds the most, 583. Precipitation totals 39.0 inches a year, most in May (4.5") and least in February (2.0"); May to September bring 47% of it.

The nearest other station, Montague 4 NW, MI, 10 miles south of Shelby, has a last frost 7 days later (May 19), a first frost 6 days earlier (October 4), a season 15 days shorter.

The first measurable snow (0.1 inch or more) in Shelby usually arrives around November 16, and the last of the season around April 3. Those are the middle dates across the winters of 1991–2020 at Hart 3 WSW, MI, 5.4 miles away: half of years saw snow earlier, half later. Every one of those winters saw snow. The last 32°F night of spring typically comes 39 days after the last snow.

ZIP 49455 is 5 miles from Hart 3 WSW, MI, which stands at 770 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 1 other ZIP code shares the station; its figures are presented in full for 49420 (Hart). The 2023 USDA Plant Hardiness Zone Map lists ZIP 49455 in zone 6a, the band where the coldest night of the year averaged -10 to -5°F (-23.3 to -20.6°C) over 1991–2020; a zone describes winter lows, not frost dates.